Impedance spectrum of a modern flute with a C foot measured at the embouchure
hole using fingering for C7.
Z is plotted in dB, i.e. 20 log(Z/Pa.s.m-3).

This fingering is comparable to that for F4 except for
the use of one of the G# keys and the LH thumb key as register
holes. Comparing this with the F4 impedance spectrum,
we see that the fifth minimum is a little deeper. The first minimum plays ~C5
and the second ~B5 but, because it is a cross fingering for these notes, their
timbres are darker. Combinations of these three notes may be played simultaneously
as multiphonics. Compare the impedance spectrum with that for C7
on a flute with a B foot, whose working minimum is several dB deeper. The
enhanced ease of playing C7 softly is an advantage of the B foot.

Sound

Sound spectrum
of a modern flute with a C foot played using fingering for C7.